Many kinds of fossils other than plants and insects are found in the Mazon Creek-Braidwood area of Illinois, and among them are the horseshoe crabs. These marine animals were much like their present-day relatives and must have lived in shallow seas just offshore from Coal Age forests. A relatively few specimens have been found in Illinois. All are of Pennsylvanian age and came from the Mazon Creek area.
See horseshoe crabs: plate 21 (center right of image).
The printed version of Guide for Beginning Fossil Hunters can be purchased from the Shop ISGS Web site.
Updated 09/23/2011 SLD